In the screen printing of garments, in order to obtain high quality products it is necessary that the screen be properly aligned with the platen. This is especially important in multi-color printing in which it is necessary that each screen, for each different color, have the indicia (to be printed on the garment) thereon properly positioned with respect to each of the other screens and platen so that as each screen is moved into association with the platen the indicia from the screen is properly aligned to print a clear, high quality image on the garments.
In order for registration to be effected successfully, it is necessary to register the multi-color positives with respect to each other, and there must be an accurate relationship between where the image transferred from the positive to the screen falls with respect to the platen.
The most common method in use for registering screens to the printing machines is to tape each positive onto the platen, and then align the screen to the positive. When the screen is in position over the positive the screen is fastened into position using the conventional knobs provided on the screen printing machine. In order to be successful, the person practicing the method must exercise extreme care, have patience, and take his or her time. Good light is also necessary. One of the many problems encountered in practicing the method is that when the knobs are tightened the torsional force of the knobs turning creates a creep in the screen frame causing it to move out of registration.
Another commonly utilized method is often referred to as micro-registration. There are a number of commercially available products for effecting micro-registration, allowing minor adjustment to align the screen with the positive. Using these devices, too, however, the operator needs a good eye and must have the time and patience to do a good job.
Another commercially available machine uses a plug-in registration system. In this system, the screen arms on the machine must all come down exactly to the same position. If for any reason any one of the arms do not come down in the same position, such as due to wear, the machine will be out of registration. The film positives are placed in registration with the machine by aligning the positives in a dark room with dowels or with a grid, with each positive aligned to its respective frame in exactly the same way in the dark room. Wooden frames cannot be utilized, but rather only aluminum frames have the necessary dimensional stability. The assumption is made in this system that because the positives are all exposed in exactly the same way in registration to the screen frames that the same registration will result on the screen printing machine; however if due to wear, or other real-life factors, this assumption is incorrect, accurate registration does not ensue.
Most machines that are on the market that attempt to facilitate accurate registration are specific to one or a few pieces of equipment, and therefore cannot be employed by a high percentage of potential users.
According to the present invention, a simple method and apparatus are provided which ensure accurate registration of screens with the platen in multi-color printing. In addition to being simple yet effective, the equipment is very versatile, not being specific to the particular manufacturer of printing machinery, or the particular type of frame utilized.
According to one aspect of the present invention, a kit is provided for facilitating the accurate registration of each of a plurality of printing screens in association with a printing platen. The kit includes a registration plate having a plurality of pins upstanding from it, the pins having a predetermined size and predetermined spacing from each other; a plurality of clamps; and one or more collars. One clamp is provided for each different color to be printed (e.g. four clamps for a four color system). Each clamp has a clamping portion dimensioned to engage the frame (whether wooden or aluminum) of a screen. The clamp has an extension with a plurality of openings in it, the openings having the same size and spacing as the pins of the registration plate. The collar is attachable to the printing machine and has a plurality of upstanding pins, with the pins having the same size and spacing as the pins of the registration plate. The collar may be particularly adapted to attach to a T-shirt platen, or to a cap printer, or to the arm of the printing machine. The clamp may be designed to accommodate a cap printer with a bill support.
The invention also encompasses a method of accurately registering printing screens with a platen during multi-screen (typically multi-color) printing of a garment. The method steps are as follows: (a) Aligning a plurality of film positives having indicia thereon so that the indicia on each positive is properly aligned with the indicia on all the other positives. (b) Providing a plurality of openings in each of the positives so that the openings of all the plurality of positives are aligned with each other when the positives are aligned, the openings in each positive being of the same predetermined size, and spaced a predetermined distance from each other. (c) Mounting a clamp, having a plurality of openings the same size and spacing distance as the openings in the positives, onto the frame of each of the plurality of printing screens. (d) For each positive, assembling the positive and a screen together with the positive overlying the screen fabric and with pins, having the same size and spacing as the openings in the positive and clamp associated with the screen, passing through the openings in the positive and clamp to hold the positive and screen together in precise alignment. (e) Exposing each positive-screen assembly to transfer the indicia of the positive to the screen fabric. (f) Removing each positive from assembly with its associated screen. (g) Mounting a collar having a plurality of pins of the same size and spacing as the openings in the screen clamps, in alignment with the platen of the printing machine. (h) For each of the plurality of screens, aligning the screen in printing position with the platen by loosely mounting the screen to the printing machine, moving the screen so that the clamp overlies the collar, adjusting the position of the screen in the printing machine so that the openings in the clamp are aligned with the pins of the collar, and affixing the screen in that aligned position on the printing machine. (i) Removing the clamp from each of the screens after the practice of step (h), and before printing of garments with the screens. And, (j) marking the position of the clamp on the screen prior to the practice of step (i) so that after printing with the screen, and removal of the screen from the printing machine, the clamp may be accurately located on the screen, and thus the screen on the printing machine, if it is desired to use the screen on the machine again.
Step (b) can be practiced in a number of different ways. One way is to punch the film positives while they are properly aligned, and in a stack. Another way to practice step (b) is by overlapping each film positive with a non-film positive piece of material; making a wallpaper cut at the overlapped portions of the positive and material to provide them with adjacent edges; taping the material and positive together so that the edges abut each other; and providing the openings in the material.
The invention also encompasses component parts of the equipment described above, as well as sub-steps of the method described above.
It is the primary object of the present invention to provide a method and apparatus for accurately registering screens to a platen for the screen printing of garments and the like. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.